1. Field of the Invention
The present invention relates to an apparatus for rapidly loading and unloading cargo containers from a vessel, such as a ship and transporting them to a storage or ground transport area.
2. Description of the Prior Art
In the past decade and a half, much of the marine cargo industry has been converted to containerized cargo wherein products to be shipped are loaded in large containers of a size approaching that of a conventional truck cargo van and then loading the filled containers themselves on the ships. Such a containerized approach has prove popular and allows for loading and unloading thereof inland of the dock and subsequent transportation of such containers to and from the dock area for loading on a vessel. This allows for economical loading of the individual containers at a rate dictated by convenience and uninfluenced by the significant cost of lay time for a sea going vessel which must be at dock for the final loading process. Likewise, when such containers are unloaded from the vessel they may be transported by truck or train, fully loaded, to their destination where the unloading process of the containers themselves will take place.
Due to the fact that the hourly cost of a ship in harbor is considerable, many efforts have been made to provide for rapid loading and discharging of such cargo containers from the ship to thereby minimize the time a ship must remain in port for discharge and loading. One such cargo handling apparatus in common use utilizes a hoist mounted on a trolley carried on an overhead boom of a hammer head crane wherein the hoist may be attached to a container to hoist such cargo up to the trolley to be transported across the boom to be disposed over the hatchway to the ship's hold. The hoist is then actuated to lower the container into the hold. The process is then repeated until the ship's hold is filled. A hatch cover is then placed in position over the hatchway and additional containers then stacked on the hatch to a height of, for instance, four to five containers and seven to twelve athwartship, each container having a height on the order of eight feet.
Such system suffers the shortcoming that the trolley must be positioned over the container on the dock, the hoist lowered a distance of, for instance, 150 feet and attached to the container. The container must then be hoisted upwardly the same distance of 50-65 feet, and the trolley then transported out the boom and over the ship. Again, there, the container is lowered into the ship's hold or onto the deck of the ship and the process repeated. Unloading of the ship is just the reverse. That is, the containers are picked up, first off the stack loaded on the ship's deck, the hatch cover removed and then the containers removed from the hold. It will be appreciated that the time consumed each time the hoist is raised and lowered is significant and that the trolley is fully occupied by a single container during the entire transfer procedure. In addition to the time consumption, such systems typically require a substantial amount of support equipment and personnel. That is, a crane driver is required for the trolley on the hammerhead crane, ship deckmen are required for attaching and detaching the cargo hoist, tractor or truck drivers are required for sequentially moving trucks, bogies or straddle trucks onto the dock area for receiving the cargo containers and removing them from the hoist area during the discharge operation. The need for more economical and efficient systems have led to many different proposals.
One such system involves a pair of vertical conveyors, one dock side and another ship side, with a horizontal conveyor therebetween for automatically transferring pelletized loads up from the ship's hold, across the horizontal conveyor and down to the dock. An arrangement of this type is shown in U.S. Pat. No. 1,525,950 to Prescott. Such devices, while acceptable for their intended use, suffer the shortcoming that they cannot practically handle large containers typically used in maritime shipping and that their operation is hindered by surge and rise and fall of the tide which results in misalignment of the conveyors and renders transfer from one conveyor to the other impossible.
Other devices proposed include a horizontal hammerhead crane carrying a trolley mounting a hoist which is intended to pick up cargo from the ship to be lowered into a vertical elevator for subsequent transfer. A device of this type is shown in U.S. Pat. No. 4,431,359 to Toniolo. Again, while satisfactory for its intended purpose, such devices suffer the shortcoming that the elevators are not configured and arranged to receive the cargo containers sideways thereonto from the hoist without substantial lowering thereof each time transfer is made thus consuming undue time. Accordingly, substantial time is lost on each trip because of the necessity that the hoist raise the container to the full height so the trolley may carry it to a position disposed over the elevators so the cargo may be lowered some distance thereonto.
Accordingly, there exists a need for a cargo handling system which provides for efficient movement of the trolley on the hammerhead crane with a minimum of down time for retrieving cargo containers from the ship's deck at approximately the elevation of the cargo's initial storage and transfer substantially horizontally directly to elevators located at about the same height so that vertical travel of the hoist is minimized to make most efficient use of the trolley.